night blindness (vitamin A deficiency)

Vitamin A deficiency is a lack of <a href="http://en.wikipedia.org/wiki/Vitamin_A" title="Vitamin A" >vitamin A</a> in humans. It is common in developing countries but rarely seen in developed countries. <a href="http://en.wikipedia.org/wiki/Night_blindness" title="Night blindness" class="mw-redirect" >Night blindness</a> is one of the first signs of vitamin A deficiency.

<a href="http://en.wikipedia.org/wiki/Xerophthalmia" title="Xerophthalmia" >Xerophthalmia</a>, <a href="http://en.wikipedia.org/wiki/Keratomalacia" title="Keratomalacia" >keratomalacia</a>, and complete blindness can also occur since Vitamin A has a major role in<a href="http://en.wikipedia.org/wiki/Visual_phototransduction" title="Visual phototransduction" >phototransduction</a>. Approximately 250,000 to 500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A, approximately half of whom die within a year of becoming blind. The <a href="http://en.wikipedia.org/wiki/United_Nations" title="United Nations" >United Nations</a> Special Session on Children in 2002 set the elimination of vitamin A deficiency by 2010. The prevalence of <a href="http://en.wikipedia.org/wiki/Night_blindness" title="Night blindness" class="mw-redirect" >night blindness</a> due to vitamin A deficiency is also high among pregnant women in many developing countries. Vitamin A deficiency also contributes to <a href="http://en.wikipedia.org/wiki/Maternal_mortality" title="Maternal mortality" class="mw-redirect" >maternal mortality</a> and other poor outcomes in <a href="http://en.wikipedia.org/wiki/Pregnancy" title="Pregnancy" >pregnancy</a> and <a href="http://en.wikipedia.org/wiki/Lactation" title="Lactation" >lactation</a>.<a href="http://en.wikipedia.org/wiki/Vitamin_A_deficiency#cite_note-WHO_Vitamin_A_deficiency.7C_Micronutrient_deficiencies-0" >[1]</a><a href="http://en.wikipedia.org/wiki/Vitamin_A_deficiency#cite_note-isbn92-5-103818-X-1" >[2]</a><a href="http://en.wikipedia.org/wiki/Vitamin_A_deficiency#cite_note-isbn92-4-154478-3-2" >[3]</a><a href="http://en.wikipedia.org/wiki/Vitamin_A_deficiency#cite_note-A_world_fit_for_children-3" >[4]</a>

Vitamin A deficiency also diminishes the ability to fight infections. In countries where children are not <a href="http://en.wikipedia.org/wiki/Immunization(medicine)" title="Immunization (medicine)" class="mw-redirect" >immunized</a>, infectious disease like <a href="http://en.wikipedia.org/wiki/Measles" title="Measles" >measles</a> have higher fatality rates. As elucidated by <a href="http://en.wikipedia.org/wiki/Alfred_Sommer(ophthalmologist)" title="Alfred Sommer (ophthalmologist)" class="mw-redirect" >Dr. Alfred Sommer</a>, even mild, subclinical deficiency can also be a problem, as it may increase children's risk of developing respiratory and diarrheal infections, decrease growth rate, slow bone development, and decrease likelihood of survival from serious illness.

Vitamin A deficiency is estimated to affect approximately one third of children under the age of five around the world.<a href="http://en.wikipedia.org/wiki/Vitamin_A_deficiency#cite_note-4" >[5]</a> It is estimated to claim the lives of 670,000 children under five annually.<a href="http://en.wikipedia.org/wiki/Vitamin_A_deficiency#cite_note-5" >[6]</a> Approximately 250,000-500,000 children in developing countries become blind each year owing to vitamin A deficiency, with the highest prevalence in Southeast Asia and Africa. According to the World Health Organization (WHO), vitamin A deficiency is under control in the United States, but in developing countries vitamin A deficiency is a significant concern.